The article presents the results of tests on the lubricity properties of SN150 base oil containing
hexagonal boron nitride (h-BN) of different granulation. The boron nitride with a particle size below
100 nm and the second one with a particle size below 25 μm were used. The lubricity tests were carried
out on a four-ball apparatus. The methodology of these tests was determined on the basis of the normative
document PN-EN ISO 20623: 2018-02, which contains the following parameters characterising the
lubricity: initial seizure load ISL [N], weld load WL [N], load-wear index LWI [N], mean wear scar
diameter MWSD [mm] obtained in a long duration wear test under a specified load; wear-load curve,
i.e., the dependence of the mean wear scar diameter on the load, was also performed. Tests were also
carried out to check the influence of selected surfactants on the sedimentation process of hexagonal
boron nitride in the SN150 mineral base oil. Based on the conducted research and their analysis, it
was found that hexagonal boron nitride has a positive effect on the lubricating properties of the base
oil; better results were obtained for the boron nano-nitride with a particle size below 100 nm. It was
also found that the problem of sedimentation of the solid particles of hexagonal boron nitride was
solved by the addition of succinimide dispersant.
Keywords: tribology, lubricity, boron nitride, surfactants, sedimentation